[PATCH 0/5] rcu: Record callback enqueue stacks and add torture tests

[Kunwu Chan <kunwu.chan@gmail.com>]

This series adds KASAN auxiliary stack recording for RCU Tasks
callbacks, rcutorture coverage for duplicate-callback detection,
and KASAN aux-stack verification tests across RCU and SRCU flavors.

This series is based on [1]. For testing, I also applied Joel
Fernandes' fix for debugobjects tracking of barrier callbacks
[2], which is needed for the barrier tests.

The changes:
- Record the enqueueing stack in call_rcu_tasks_generic().
- Enable duplicate-callback testing for the "tasks" and
  "tasks-tracing" torture types.
- Add a KASAN aux-stack verification test module with a Kconfig
  choice for each supported flavor.
- Add one rcutorture scenario per flavor for the verification
  test.

Tested on x86_64:

- TASKS01, TASKS02, TASKS03, TRACE01, and TRACE02 completed
  3-minute runs successfully.

- With CONFIG_DEBUG_OBJECTS_RCU_HEAD=y and
  rcutorture.object_debug=1, duplicate-callback detection was
  triggered as expected for both torture types.

- TRACE01 was run for 1 minute with
  CONFIG_DEBUG_OBJECTS_RCU_HEAD=y and
  rcutorture.object_debug=1. The test detected both duplicate
  callback heads through the SRCU enqueue path:
[    0.405836] rcutorture: WARN: Duplicate call_tasks-tracing() test starting.
[    0.405852] ODEBUG: activate active (active state 1) object: 0000000020df980d object type: rcu_head hint: 0x0
[    0.734724] rcu: __call_srcu(): Duplicate call_srcu() CB 0000000020df980d->rcu_torture_leak_cb+0x0/0x10()
[    0.734780] ODEBUG: activate active (active state 1) object: 000000006634e8c9 object type: rcu_head hint: 0x0
[    0.776688] rcu: __call_srcu(): Duplicate call_srcu() CB 000000006634e8c9->rcu_torture_leak_cb+0x0/0x10()
[    0.779126] rcutorture: WARN: Duplicate call_tasks-tracing() test complete.
[   65.411342] tasks-tracing-torture:--- End of test: SUCCESS: ...

Both duplicate callback heads (the stack-allocated rh2 and
the kmalloc-allocated rhp) were rejected and neither was invoked.

- With CONFIG_DEBUG_OBJECTS_RCU_HEAD=y,
  object_debug=1, and n_barrier_cbs=4, the TASKS01 barrier
  test completed 630/630 rounds without barrier errors.
  The only debugobjects warnings were the four intentional
  warnings from the duplicate-callback test at startup.

- All five aux-stack scenarios (TASKSKASAN01, TREEKASAN01,
  SRCUKASAN01, TINYKASAN01, and SRCUTINYKASAN01) produced the
  expected KASAN use-after-free reports. Each report's
  "Last potentially related work creation" entry showed the
  expected enqueue helper:

===== TASKSKASAN01 =====
[    1.244567] BUG: KASAN: slab-use-after-free in aux_test_init+0x8d/0xb0
[    1.244707] Last potentially related work creation:
[    1.244716]  aux_test_call_rcu_tasks.constprop.0+0xc/0x20

===== TREEKASAN01 =====
[    0.670399] BUG: KASAN: slab-use-after-free in aux_test_init+0x8d/0xb0
[    0.670561] Last potentially related work creation:
[    0.670571]  aux_test_call_rcu_tree.constprop.0+0xc/0x20

===== SRCUKASAN01 =====
[    0.658679] BUG: KASAN: slab-use-after-free in aux_test_init+0x94/0xc0
[    0.658919] Last potentially related work creation:
[    0.658932]  aux_test_call_srcu.constprop.0+0x16/0x30

===== TINYKASAN01 =====
[    0.951503] BUG: KASAN: slab-use-after-free in aux_test_init+0x8d/0xb0
[    0.951641] Last potentially related work creation:
[    0.951650]  aux_test_call_rcu_tiny.constprop.0+0xc/0x20

===== SRCUTINYKASAN01 =====
[    1.009005] BUG: KASAN: slab-use-after-free in aux_test_init+0x94/0xc0
[    1.009141] Last potentially related work creation:
[    1.009150]  aux_test_call_srcu.constprop.0+0x16/0x30


These reports are intentional and are counted as runtime
errors by rcutorture.

[1] https://lore.kernel.org/all/20261027070923.3054462-1-kunwu.chan@gmail.com/
[2] https://lore.kernel.org/all/20261104153046.965890-1-joelagnelf@nvidia.com/

Kunwu Chan (5):
  rcu-tasks: Record callback enqueue stack
  rcutorture: Test duplicate call_rcu_tasks() callback enqueue
  rcutorture: Test duplicate call_rcu_tasks_trace() callback enqueue
  rcu: Add KASAN aux-stack verification test
  rcutorture: Add KASAN aux-stack verification scenarios

 kernel/rcu/Kconfig.debug                      |  38 +++++++
 kernel/rcu/Makefile                           |   1 +
 kernel/rcu/rcu_kasan_aux_test.c               | 107 ++++++++++++++++++
 kernel/rcu/rcutorture.c                       |   2 +
 kernel/rcu/tasks.h                            |   4 +
 .../rcutorture/configs/rcu/SRCUKASAN01        |   6 +
 .../rcutorture/configs/rcu/SRCUKASAN01.boot   |   2 +
 .../rcutorture/configs/rcu/SRCUTINYKASAN01    |  12 ++
 .../configs/rcu/SRCUTINYKASAN01.boot          |   2 +
 .../rcutorture/configs/rcu/TASKSKASAN01       |  13 +++
 .../rcutorture/configs/rcu/TASKSKASAN01.boot  |   2 +
 .../rcutorture/configs/rcu/TINYKASAN01        |  12 ++
 .../rcutorture/configs/rcu/TINYKASAN01.boot   |   2 +
 .../rcutorture/configs/rcu/TREEKASAN01        |   6 +
 .../rcutorture/configs/rcu/TREEKASAN01.boot   |   2 +
 15 files changed, 211 insertions(+)
 create mode 100644 kernel/rcu/rcu_kasan_aux_test.c
 create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/SRCUKASAN01
 create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/SRCUKASAN01.boot
 create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/SRCUTINYKASAN01
 create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/SRCUTINYKASAN01.boot
 create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/TASKSKASAN01
 create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/TASKSKASAN01.boot
 create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/TINYKASAN01
 create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/TINYKASAN01.boot
 create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/TREEKASAN01
 create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/TREEKASAN01.boot

-- 
2.43.0